title: In vivo disposition and metabolism of madecassoside, a major bioactive constituent in Centella asiatica (L.) Urb.
abstract: BACKGROUND
  Centella asiatica (L.) Urb. herb is frequently used in traditional Chinese medicine for many indications, such as traumatic injuries, keloid and scar. Madecassoside is the main active ingredient of this herb drug with higher content than other triterpenoid constituents. Understandings of pharmacokinetic profiles of madecassoside should be beneficial for its development as a therapeutic agent.
  
  
  METHODS
  Sprague-Dawley rats were intravenously and orally administered madecassoside (100 mg/kg), respectively. Plasma, heart, liver, spleen, lung, kidney, brain, bile, urine and feces were collected at the designed time points. Madecassoside concentrations in biological samples were determined by a sensitive and well-validated liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method. A liquid chromatography coupled with time-of-flight mass spectrometry (LC-TOF-MS) method was established to identify its major metabolites in feces. To further pursue the disposition characteristics of madecassoside in rats, the involvement of the hepatobiliary efflux transporters in biliary elimination were studied by combination with digoxin (P-glycoprotein inhibitor) or probenecid (multidrug resistance-associated protein inhibitor). A linked-rat model was also used to assess the role of enterohepatic circulation in the pharmacokinetics of madecassoside.
  
  
  RESULTS
  After a single oral dosing, madecassoside was widely distributed in heart, liver, spleen, lung and kidney of rats, and the levels of madecassoside in liver and kidney were relatively higher than other organs. The excretions of madecassoside in bile, urine and feces were 7.16% (0-12 h), 0.25% (0-72 h) and 24.68% (0-72 h), respectively. The findings suggested that madecassoside might excrete mainly by metabolites. The combination with either digoxin or probenecid significantly attenuated the excretion of madecassoside as parent from bile, indicating that P-glycoprotein and multidrug resistance-associated protein might contribute to the hepatobiliary elimination of madecassoside. The presence of enterohepatic circulation, as implied by double-humped profiles in plasma and tissue concentration-time curves, was confirmed by a linked-rat model. Furthermore, three metabolities of madecassoside were indentified in rat feces and the possible metabolic pathways were proposed.
  
  
  CONCLUSIONS
  These findings provide valuable information regarding in vivo process of madecassoside, and help us to recognize the efficacy and safety of madecassoside itself, the relevant herbs or herbal preparations.
authors.affiliation: State Key Laboratory of Natural Medicines, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing 210009, China; Department of Chinese Materia Medica Analysis, China Pharmaceutical University, 24 Tong Jia Xiang, Nanjing 210009, China.
authors.forename: Dan-dan
authors.initials: DD
authors.lastname: Leng
authors.forename: Wen-jing
authors.initials: WJ
authors.lastname: Han
authors.forename: Yao
authors.initials: Y
authors.lastname: Rui
authors.forename: Yue
authors.initials: Y
authors.lastname: Dai
authors.forename: Yu-feng
authors.initials: YF
authors.lastname: Xia
mesh_terms: D000818:Animals; D001646:Bile / Q000737:chemistry; D001921:Brain / Q000378:metabolism; D028041:Centella; D005243:Feces / Q000737:chemistry; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013154:Spleen / Q000378:metabolism; D014018:Tissue Distribution; D014315:Triterpenes / Q000097:blood / Q000493:pharmacokinetics* / Q000652:urine
chemical_list: D014315:Triterpenes; C093443:madecassoside
keywords: Enterohepatic circulation; Excretion; Hepatobiliary transporter; IS; Internal standard; LC-TOF-MS; LLOQ; Liquid chromatography coupled with time-of-flight mass spectrometry; Lower limit of quantification; MRP2; Madecassoside; Metabolism; Multidrug resistance-associated protein; P-glycoprotein; P-gp; QC; Quality control; Tissue distribution